In the wake of the violent clashes between police and protesters in Ferguson, Missouri, Sen. Claire McCaskillhas announced she will head a Senate hearing investigation into the "militarization of local police departments."

Police in the St. Louis suburb have been attacked for using former military equipment to help quell the riots that followed the shooting death of unarmed black teenager Michael Brown by white police officer Darren Wilson.

McCaskill, the Democratic chairwoman of the Homeland Security and Governmental Affairs' Financial and Contracting Oversight subcommittee, said her panel would study the Pentagon's 1033 program that allows local police departments to buy surplus military equipment at discounted prices.

The hearing would also examine Department of Homeland Security grants to local police departments to help them acquire military-style equipment, the senator said.

Homeland Security has handed out six-figure grants to towns and cities across the U.S., which have helped to fund the purchase of BearCats and other heavily-fortified vehicles since the 2001 terrorist attacks, according to The Wall Street Journal.

Last year the government also gave out 200 surplus vehicles built to withstand mines and bombs in Iraq and Afghanistan, and is mulling over requests from 750 more communities, the Journal said.

More than $4 billion worth of discounted military ware, including M16s and mine-resistant vehicles, has been sold to police departments nationwide since the 1033 program started, The Hill reported.

During the protests in Ferguson, McCaskill criticized heavily-armed police for pointing mounted machine guns at demonstrators, and called for authorities to "de-militarize the situation."

In the past seven years, Ferguson has received two Humvees, a generator and a cargo trailer from the military, The Hill said citing a report from the Pentagon, which also noted that St. Louis County has received three helicopters, seven Humvees, a bomb detecting robot, six pistols and 12 rifles.

Democratic congressman Rep. Hank Johnson of Georgia is planning to introduce legislation in September to cut back on the Pentagon program, The Hill reported.

"As the tragedy in Missouri unfolds, one thing is clear: our local police are becoming militarized," Johnson said last week. And in a letter to members of Congress, he wrote, "Our main streets should be a place for business, families, and relaxation, not tanks and M16s."

In a Time column, Kentucky Sen. Rand Paul said that Washington had "incentivized the militarization of local police precincts" by providing money to help local governments build "what are essentially small armies."

Conservative radio host Rush Limbaugh also accused the Pentagon of militarizing police departments. "Where do you think the militarization equipment comes from for these police departments? It comes from the U.S. Department of Defense, the DOD," Limbaugh said.

Attorney General Eric Holder has criticized the use of war-zone equipment during the Ferguson unrest, according to Politico, while President Barack Obama has weighed in on the issue as well, suggesting that the program providing military arms to local law enforcement may have gone too far.

"I think one of the great things about the United States has been our ability to maintain a distinction between our military and domestic law enforcement," Obama said during a news conference while on vacation in Martha's Vineyard, Mass.

"I think it's probably useful for us to review how the funding has gone, how local law enforcement has used grant dollars, to make sure that what they're purchasing is stuff that they actually need, because there is a big difference between our military and our local law enforcement and we don't want those lines blurred."

In the wake of the violent clashes between police and protesters in Ferguson, Missouri, Sen. Claire McCaskill has announced she will head a Senate hearing investigation into the militarization of local police departments.